While I agree that JJ has never shown the leadership and "taking a game over" abilities that I consider requisite to becoming a superstar/max player, to say that he will absolutely never end up there is probably premature. This week he has elevated his game into a whole new level and led his bumbling mess of a team to 4 wins out of there last 5, with about three of those wins coming over quality opponents, including the Spurs, the Cavs, and Memphis. He won player of the week honors for the East this week while posting numbers of 25-7-6.3 - pretty much the best overall numbers in the league during that period. More importantly, it has been his leadership this week that has resulted in the wins, and he has executed during crunch time to pull out a couple of the closer wins.
Now that is admittedly a very small sample size, and it is pretty unlikely that he will produce at that level on a consistent basis, and even more unlikely that the Hawks will continue to win (in fact, I hope they don't, because we have draft picks waiting on that). But the fact is, that, at least for one week, JJ has played like a superstar/max player. He has shown he has the ability to perform at that high of a level, so to say that he will never become that kind of player is probably premature.
The biggest shock to me is if he ever became a true leader. His personality just doesn't seem fit for that. But if Tim Duncan wasn't so immensely talented and successful, would he be viewed as a leader?